Fixes nova-manage fixed list.
Fixes nova-manage fixed list.

Updates the nova-manage to use db.instance_get_all for instance
information instead of relying on Sqlalchemy model relationships
(which no longer exist due to network refactorings).

This commit fixes 'nova-manage fixed list' so that it correctly
displays hostname, and host. I dropped the MAC address column
which would have required an extra VIF's table lookup and
wasn't used as much.

Fixes LP Bug #920159.

Change-Id: I3cec690c5e40631e0f10b2a914f46863601a1734

n0ano/gantt,n0ano/gantt